Presented at RubyConf 11/10/2013 Introduced in Ruby 2.0, TracePoint is meant to help developers better instrument their code for debugging and performance reasons, but there's more to TracePoint than that! In this talk we'll learn about TracePoint while building several example projects. Once we know the basics we'll use TracePoint to do things to Ruby that we couldn't have done otherwise. By the end of this talk you'll be able to frighten and amaze your friends when you show them things like true abstract classes and interfaces in Ruby, just like Java! Yikes!

1. @markbates

4. http://mo.markbates.com

6. RUBYCONF13
http://www.metacasts.tv

7. Mangling Ruby
with TracePoint

8. TracePoint

10. trace = TracePoint.new(:raise) do |tp|
p [tp.lineno, tp.event, tp.raised_exception]
end
#=> #<TracePoint:0x007f786a452448>
!
trace.enable
#=> #<TracePoint:0x007f786a452448>
!
0 / 0
#=> [5, :raise, #<ZeroDivisionError: divided by 0>]

11. Events

12. TracePoint.new(:class)
TracePoint.new(:end)

13. TracePoint.new(:call)
TracePoint.new(:return)
TracePoint.new(:c_call)
TracePoint.new(:c_return)

14. TracePoint.new(:raise)

15. TracePoint.new(:b_call)
TracePoint.new(:b_return)

16. TracePoint.new(:thread_begin)
TracePoint.new(:thread_end)

17. Demo

18. Method Call
Collector

24. TracePoint:
disable
enable
1
1
Object:
puts
at_exit
1
1
!
!
Class:
new
method_added
inherited
1
1
1
Foo:
bar
initialize
1
1
IO:
write
puts
2
1
Symbol:
to_proc
1
Array:
map
1
!
!
!
!
------------Totals:
Class
3
IO
3
Object
2
TracePoint 2
Foo
2
Symbol
1
Array
1
!
!
Total Method Calls: 14

26. Total Method Calls: 122538

27. Class
Rails::Initializable::Initializer
Symbol
Module
String
Array
Hash
Fixnum
Object
ActionDispatch::Journey::Visitors::Each
File
Rails::Paths::Path
Regexp
ThreadSafe::Cache
25888
16502
14136
12727
11379
6080
4479
3108
2499
2276
1888
1655
1190
1026

28. HelloController:
class
process_action
lookup_context
initialize
instance_variable_defined?
method_for_action
respond_to?
render
_normalize_options
render_to_body
_process_options
block_given?
dispatch
view_renderer
_render_template
process
append_info_to_payload
_prefixes
response_body=
config
instance_variable_get
_normalize_args
cleanup_view_runtime
13
7
4
4
4
3
3
3
3
3
3
2
2
2
2
2
2
2
2
2
2
2
2

31. Demo

34. jRuby

35. Abstract Interfaces
IN RUBY!

36. Please Don’t!
Actually Do This!

38. interface Bicycle {
void changeGear(int newValue);
void speedUp(int increment);
void applyBrakes(int decrement);
}
!
public class ACMEBicycle implements Bicycle {
public void changeGear(int newValue) {
// do some work here
}
public void speedUp(int increment) {
// do some work here
}
public void applyBrakes(int decrement) {
// do some work here
}
}

39. module ApiInterface
include AbstractInterface
abstract_method :get, :put
end
!
class HttpLibrary
include ApiInterface
end

40. module ApiInterface
include AbstractInterface
abstract_method :get, :put
end
!
class HttpLibrary
include ApiInterface
end

41. module ApiInterface
include AbstractInterface
abstract_method :get, :put
end
!
class HttpLibrary
include ApiInterface
def get
end
def put
end
end

49. module ApiInterface
include AbstractInterface
abstract_method :get, :put
end
!
class HttpLibrary
include ApiInterface
end

50. @markbates
http://www.metacasts.tv